Snowmobile exhaust arrangement

ABSTRACT

A snowmobile is provided at a lower front portion with a well defined by a main front plate projecting downward from the front end of the top plate of an inverted channel shaped main frame, a forwardly progressively elevated front bottom plate having a rear end connected with the lower end of the main front panel and a pair of front side plates extending lengthwise of the main frame, the lower edge of each of the front side plates being connected with the front bottom plate, wherein an exhaust silencer for silencing the noises caused by exhaust gases from an internal combustion engine mounted on the main frame is disposed in the well.

United States Patent [191' Base [ Mar. 11, 1975 [73] Assigneez- YamahaHatsudoki Kabushiki Kaisha, Shizuoka-ken, Japan [22] Filed: May 11, 1973[21] Appl. No.: 359,334 v [30] Foreign Application Priority Data May 13,1972 Japan 47-55730 [52] U.S. Cl. ..'l80/5 R, 180/64 A [51] Int. Cl B60k13/06 [58] Field of Search 1,80/5 R, 54 A, 64 A;

[5 6] References Cited UNITED STATES PATENTS 3,382,948 5/1968 Walker etal. 181/35 B 3,779,327 12/1973 Pereault 180/64 A Primary ExaminerRobertB. Reeves Assistant ExaminerLarry H. Martin [57] ABSTRACT A snowmobileis provided at a lower front portion with a well defined by a main frontplate projecting downward from the front end' of the top plateof aninverted channel shaped main frame, a forwardly progressively elevatedfront bottom plate having a rear endconnected with the lower end of themain front panel and a pair of front side plates extending lengthwise ofthe main frame, the loweredge of each of the front side plates beingconnected with the front bottom plate, wherein an exhaust silencer forsilencing the noises caused by exhaust gases from an internal combustionengine mounted on the main frame is disposed in the well.

3'Claims, 4 Drawing Figures llbllo ll PATENTEUHARI 1 1915 saw 1 or 4FIG.

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mm wv ww mv mm in mm m GE PATENTEB HARI 1 I975 sum u or 4 & mm \J, y l mm E a w E n m m u u n m P mi mi N N Q15, Em wm mm m m 9 Km El Q m mm mm0% 6 Q km 5 mm mm Ev EN mm h mm Ev SNOWMOBILE EXHAUST ARRANGEMENTBACKGROUND OF THE INVENTION This invention relates to a snowmobilecapable of carrying one to three persons and more particularly to such asnowmobile in whichan exhaust silencer is positioned in a well locatedat a forward lower portion thereof.

DESCRIPTION OF PRIOR ART In a conventional snowmobile driven by anendless track, an internal combustion engine which drives the endlesstrack is placed in a cowling which defines a front upper portion of thesnowmobile. This requires that various elements associated with theengine be also placed in a limited space defined by the cowling. Tosatisfy this requirement, it has been necessary to select the shape ofthe cowling to increase said space or to make compact the elementsassociated with the engine.

An increase in the space within the cowling or miniaturization of theengine-associated elements, however, is necessarily subjected tolimitation. In contradiction to the requirement pointed out above, alarge exhaust silencer or a plural number of exhaust silencers must beprovided if the noise caused by the exhaust gas from the engine shouldbe efficiently reduced to a minimum. Providing such a silencer orsilencers in the cowling has been difficult with a prior art snowmobileof the type described. In other words, it has been impossible tosatisfactorily silence the noise caused by the exhaust gas.

Further, the space defined by a ships bottom like front bottom plate of.the body has been left merely as a dead space without utilization.

SUMMARY OF THE INVENTION An object of the invention is to provide asmall snowmobile in which a well is formed in a front bottom plate whichhas heretofore defined a deadspace in order to substantially enlarge theavailable space in the cowling and in which an exhaust silencer isplacedin the well to attain sufficient absorption of a noise.

The snowmobile according to this invention includes an inverted channelshaped main frame provided above an endless truck and extendinglengthwise thereof, said main frame comprising a top plate and a pair ofmain side plates, a main front plate positioned forwardly of the endlesstrack and projecting downwardly from the front edge of the top plate, apair of front side plates having rear ends surperposed on the forwardends of the main side plates and extending forwardly of the snowmobile,and a forwardly progressively elevated front bottom plate having itsrear end connected to the lower end of the main front plate and furtherconnected to the lower edges of the front side plates at portionspositioned inwardly of the side edges thereof.

In a well defined by the main front plate, front side plates and thefront bottom plate is provided an exhaust silencer communicating via anexhaust tube with an internal combustion engine which is positioned onthe forward end portion of a top plate of the main frame, whereby thespace at the front bottom portion of the body, which otherwise remainsas a dead space, can be fully utilized to provide a snowmobile of highnoise silencing efficiency.

BRIEF DESCRIPTION OF THE DRAWINGS DESCRIPTION OF THE PREFERREDEMBODIMENT Referring to FIG. 1, the snowmobile embodying this inventioncomprises a body 10 including a main frame 11 extending horizontallyrearwardly from the vicinity of a forward portion of the snowmobile anda cowling 12 which covers a front upper portion of the snowmobile.

The main frame 11 which is of an inverted channel shape'lies above anendless track 13 for driving the snowmobile and has a top plate Ila anda pair of main side plates 11b formed at both sides of the top plate11a. From the forward end 11c of the top plate 11a extends downwardly amain front plate 14 which may be formed integral with said top plate 11aor may be spot welded thereto (FIGS. 1 and 3).

An internal combustion engine 15 is placed within the cowling 12 bybeing secured to the forward end portion of the top plate Ila of themain frame 11. On the top plate 11a is also mounted a seat 16 whichextends rearwardly from the vicinity of the engine 15.

The endless track 13 meshes at its forward extremity with a drivingsprocket wheel 17 driven by the engine 15 and at its rear extremity witha rear sprocket wheel (not shown). Ahead of the endless track 13 areprovided a pair of skis 18 whose direction can be controlled by a barhandle 19 through a steering column 20.

Referring to FIGS. '1 to 3, a pair of forwardly extending. front sideplates 21 having an inverted letter L shaped cross section are fixedlyconnected, such as by spot welding, to the main side plates 11b of themain frame ll..The rear halves of the front side plates 21 are adaptedto cover the main side plates 1 l b, thereby reinforcing the front endof the main frame 11. As shown in FIGS. 1, 3 and 4, a front bottom plate22 which is of a ships bottom like cross section and whose bottomsurface is gradually elevated frontwardly, has its rear end 22aconnected, such as by spot welding, to the lower end 14a of the mainfront plate 14 and its front end 22b meets the forward end of thecowling 12. As viewed fromt FIG. 4, the flanged lower edges 21a of thefront side plates 21 are rigidly secured, such as by spot welding, tothe front bottom plate 22. Further, the front bottom plate 22 and thefront side plates 21 are coupled at respective forward portions by areinforcement member 23 so that they may be reinforced by each other(FIGS. 1 and 3).

In the cowling 12, a well 24 defined by the main front plate 14, frontbottom plate 22 and front side plate 21 is formed just ahead of theinternal combustion engine 15. In the well 24 is housed exhaustsilencing means 26 for diminishing the noises produced by the exhaustgas from the engine 15. The exhaust silencing means 26 is entirely orpartly housed in the well 24.

In the embodiment shown in FIG. 1, the exhaust silencing means 26comprises an exhaust silencer 27 communicating directly with the exhaustpipe and another exhaust silencer 28 connected via a connector pipe 29to said exhaust silencer 27, and said another exhaust silencer 28 isdisposed in the well 24. The entire structure of the exhaust silencingmeans 26, however, may be located in the well 24. The silencer 28 isconnected to an exhaust gas outlet 30 which projects rearwardly from thesilencer 28, passes through the main front plate 14 and is open in frontof the endless track 13.

Referring to FIGS. 2 to 4, two double-layered brackets 31 and asingle-layered bracket 32 located between said brackets 31 are mountedon the upper surface of the silencer 28. These brackets 31 and 32 haverespectively integral arms 33 and 34 each projecting horizontally fromthe corresponding top thereof (FIG. 3) and which rspectively havethrough holes 35, 36.

A stay 37 comprises two plates 37a and 37b horizontally spaced parallelwith each other but having both end portions 370 and 37d joined togetherall along them. The joined end portions 370 and 37d are connected bybolts 38 to flanges 21b formed at the upper edges of the front sideplates 21, wherebythe stay 37 is bridged across over the well 24. Asshown in FIGS. 3 and 4, three openings 39, 40 are formed in the upperplate 37a. In the lower plate 37b are similarly formed openings 41, 42which are coaxial to said openings 39, 40 but have an increaseddiameter. Nuts 43, 44 are inserted through the openings 41, 42 and fusedto'the bottom surface of the upper plate 37a in axial alignment with thecorresponding openings 39, 40. The arms 33, 34 of the brackets 31, 32 onthe silencer 28 are positioned apart from the upper surface of the stay37 respectively by those hollow cylindrical shock absorbers 45, 46 madeof an elastic material, such as, rub.- ber, which are mounted on theupper plate 38a in coaxial relationship with the openings 39, 40. Inthis case, the through holes 35, 36 in the arms 33, 34 are coaxial withthe corresponding openings 39, 40 in the upper plate 38a. Bolts 47, 48having reduced threaded por- 48a are inserted from above the arms 33, 34through the through holes 35, 36 and the shock absorbers 45, 46 topermit the threaded portions 47b, 48b to be threadably tightened by nuts43, 44, whereby, as shown in FIGS. 3 and 4, the silencer 28 is securedto the stay 37 within the well 24 by means of the bolts 47, 48 and nuts43, 44 through the brackets'3l, 32 and the shock absorbers 45, 46. Thesilencer 28 is thus resiliently suspended from the stay 37 so that anamount of vibration transmitted from the silencer 28 to the stay 37 maybe reduced or absorbed by the shock absorbers 45, 46.

In front of the stay 37 and in parallel therewith is disposed anotherstay 49 which bridges the right and left side plates 21. The stay 49has, on its upper central surface, a support 50 for the steering column20 (FIG. 1) and, on its both ends, supports 52 for carrying ski columns51 (FIG. 1) whose lower ends are pivotally connected to the skis 18.

In operation, when the driving sprocket wheel 17 is rotated by theinternal combustion engine 15, the endless track 13 is actuated to drivethe snowmobile. An exhaust gas emitted from the engine 15 is introducedvia the exhaust pipe 25 into the exhaust silencing means 26 where thenoise caused by the exhaust gas is minimized in the following manner.

The exhaust gas is first led to the silencer 27 where an amount of thenoise thereof is reduced and then sent via the connector pipe 29 intothe silencer 28 in the well 24, where such reduced amount of noise isfurther diminished before the gas is discharged under the main frame 11through the exhaust gas outlet 30. According to this invention, use ofthetwo separate silencers 27, 28 enables the noise generated by theexhaust gas to be fully lessened.

It will be clear from the foregoing that the well 24 which hasheretofore been a dead space can be utilized to promote noise absorptionefficiency for the exhaust gas by placing the silencer 28 within thewell 24 which is defined by the main front plate 14 located at theforward end of the main frame 11, the front side plates 21 and the frontbottom plate 22.forming a forward bot tom portion of the body 10. In theillustrated embodiment, only the silencer 28 has been described to beplaced within the well 24, but it should be understood that both of thesilencers 27, 28 may be housed in the well 24. Further, when only asingle silencer is sufficient for silencing the noise, such singlesilencer may be placed within the well 24. Positioning a silencer orsilencers in such a place increases the available space within thecowling l2 and such increased space can be utilized to includeadditional devices or elements associated with the operation of theengine 15, or to permit various devices to become large-sized, in theabsence of such additional elements as the silencers.

What is claimed is:

1. A snowmobile comprising:

an inverted channel shaped main frame having a top plate;

an endless track equipped under said main frame;

an internal combustion engine mounted on the front end portion of saidtop plate for driving said endless track;

a pair of front side plates connected with said main frame andprojecting forwardly therefrom;

a main front plate extending downwardly from the front end of said mainframe;

a forwardly progressively elevated front bottom plate fixed to the loweredges of said front side plates and having the rear end connected withthe lower end of said main front plate, said front bottom plate havingthe shape of the hull of a vessel;

a first exhaust silencer connected with said engine; a second exhaustsilencer connected with said first exhaust silencer and disposed in awell defined by said front side plates, main front plate and frontbottom plate, thereby utilizing the space of said well; and

a stay positioned over said well for suspending said second exhaustsilencer.

2. A snowmobile according to claim 1 wherein said stay bridges said pairof front side plates over said well and is fixed to said second exhaustsilencer.

3. A snowmobile according to claim 2 wherein there are provided, on saidsecond exhaust silencer, brackets fixed to said stay for suspending saidsecond exhaust silencer therefrom.

1. A snowmobile comprising: an inverted channel shaped main frame havinga top plate; an endless track equipped under said main frame; aninternal combustion engine mounted on the front end portion of said topplate for driving said endless track; a pair of front side platesconnected with said main frame and projecting forwardly therefrom; amain front plate extending downwardly from the front end of said mainframe; a forwardly progressively elevated front bottom plate fixed tothe lower edges of said front side plates and having the rear endconnected with the lower end of said main front plate, said front bottomplate having the shape of the hull of a vessel; a first exhaust silencerconnected with said engine; a second exhaust silencer connected withsaid first exhaust silencer and disposed in a well defined by said frontside plates, main front plate and front bottom plate, thereby utilizingthe space of said well; and a stay positioned over said well forsuspending said second exhaust silencer.
 1. A snowmobile comprising: aninverted channel shaped main frame having a top plate; an endless trackequipped under said main frame; an internal combustion engine mounted onthe front end portion of said top plate for driving said endless track;a pair of front side plates connected with said main frame andprojecting forwardly therefrom; a main front plate extending downwardlyfrom the front end of said main frame; a forwardly progressivelyelevated front bottom plate fixed to the lower edges of said front sideplates and having the rear end connected with the lower end of said mainfront plate, said front bottom plate having the shape of the hull of avessel; a first exhaust silencer connected with said engine; a secondexhaust silencer connected with said first exhaust silencer and disposedin a well defined by said front side plates, main front plate and frontbottom plate, thereby utilizing the space of said well; and a staypositioned over said well for suspending said second exhaust silencer.2. A snowmobile according to claim 1 wherein said stay bridges said pairof front side plates over said well and is fixed to said second exhaustsilencer.